Lubricated polypropylene polyethylene self-bonded nonwoven carpet backing



3,322,607 LUBRICATED POLYPROPYLENE POLYETHYLENE SELF-BONDED NONWOVEN CARPET BACKING Shee Lup Jung, Wilmington, Del, assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Aug. 17, 1964, Ser. No. 390,199 Claims. (Cl. 161-67) This application is a continuation-in-part of application Ser. No. 305,811, filed Aug. 30, 19-63, which in turn is a continuation-in-part of application Ser. No. 220,563, filed Aug. 30, 1962.

This invention is concerned with tufted carpets, and more specifically with tufted carpets having a primary and optionally a secondary backing of a continuous filament thermoplastic nonwoven fiber composition, and with a process for making such materials.

Tufted carpets are well known and widely used. Conventionally, such carpets are made with a primary backing of a woven jute fabric which serves as a base into which tufts of the carpet fiber are introduced. It is also known to further treat such structures by applying a secondary backing or coating material to the underside of the construction after the tufting operation has been completed. This secondary backing increases the firmness of the tuft in the structure, provides greater abrasion resistance and wearing power, and stabilizes the structure. The secondary backing also improves the appearance and hand of the carpet.

It has been conventional to use rubber latex and similar products as adhesives and as backing in connection with jute substrates. Other forms of construction also employ a secondary jute backing or even a kraft paper or similar structure, adhered or laminated to the primary carpet backing with an adhesive such as starch, elastomer or resin material.

It has been recognized in the art that the jute backing, while satisfactory in many ways, has certain deficiencies. Particularly, while jute is strong, it is subject to all of the weaknesses of known natural fibers, and can vary widely in quality. In addition, the supply of jute is variable and carpet producers normally must anticipate fluctuations in price, and delays in supply which require a large inventory.

The object of this invention is to provide a lubricantbearing carpet backing.

Another object is to provide such a carpet backing which has a combination of high tear and tensile strengths and which can be tufted without loss in strength.

A further object is to provide a tufted carpet of improved dimensional stability when subjected to changes in relative humidity, and when Washed or laundered.

A still further object of this invention is a carpet construction process that employs synthetic fiber backing components which provide a high degree of strength, stability and freedom from rot, mildew and other undesirable decay. 7

These and other objects will become apparent from the following disclosure.

The product of this invention is prepared in several steps. First, there is formed a nonwoven web comprising continuous synthetic organic filaments disposed in a ran dom, nonparallel fashion. The web is preferably substantially free from filament aggregates which factor contributes significantly to the improved covering power and high strength. Filaments having a denier of between about 3 and d.p.f. are employed. The filaments may be crimped or straight and may be round in cross-section or of different shapes such as trilobal. Filaments of polymers selected from the group consisting of isotactic poly- 3,322,607 Patented May 30, 1967 propylene, linear polyethylene, crystalline copolymers of at least propylene or ethylene with up to 25% of other copolymerizable monomers and mixtures of isotactic polypropylene or linear polyethylene with up to 25% of other polymers, preferably hydrocarbon (e.g., atactie polypropylene, branched polyethylene, polyisobutylene) are useful for this invention. The process of British Patent 932,482 is especially suitable for the formation of the nonwoven webs used in the preparation of the nonwoven sheets of this invention.

Second, the nonwoven web is exposed to bonding conditions so as to produce a bonded sheet having a multiplicity of bonds of such strength that, during tufting of the sheet after lubrication as described hereinbel-ow, filament breakage is minimized. It is believed that such bonded sheets permit the filaments to be displaced and bond breakage to occur as the tufting needles penetrate the sheet. Thus, for the most part, the filaments remain intact and accordingly, the sheet retains sufficient strength for subsequent processing steps.

Bonded sheets prepared as above, however, are still found to give unsatisfactory results upon tufting. Surprisingly, it has been found that the application of a suitable lubricant to the sheets makes a substantial improvement. This result was completely unobvious in view of the fact that those skilled in the art had not heretofore lubricated carpet backing prior to tufting. Thus, as a third and essential step, there is applied to the bonded sheet a fabric lubricant such as methyl hydrogen polysiloxane, dimethyl polysiloxane, Z-ethylhexylsilicate, 2-ethylhexyl sebacate, dioctyl sebacate, acetyl 2-ethylhexyl citrate, refined coconut oil, potassium oleate, potassium n-octyl phosphates, diethanolarnine salts of 0 -0 alkyl hydrogen phosphates and mixed n-octyl B-hydroXy-ethyl esters of phosphoric acid, in an amount such that at least 0.3% and up to 5% lubricant based on the nonwoven sheet is present on the surface of the filaments at the time of tuftmg.

The lubricated backing is tufted with conventional carpet yarns, preferably at a stitch spacing of between 4 and 15 stitches per inch (1.6 to 5.9 per cm.) using tufting needles having a diameter of from 0. to 0.180 inch (0.254 to 0.457 cm.). A latex adhesive may be applied if desired to bond the tufts'in place and a secondary backing can be laid against and adhered to the primary backing by the same adhesive.

Conventional carpet backing material of jute is of the order of 0.030 to 0.045 in. (0.076 to 0.114 cm.) thick. The continuous filament nonwoven structures used as backing in the present invention are from 0.005 to 0.030 in. (0.013 to 0.076 cm.) thick, and preferably in the range of 0.010 to 0.025 in. (0.025 to 0.064 cm.) thick. The properties of a carpet depend in part upon the quantity of surface pile. Pile which is inaccessible for use, by virtue of being buried within the backing and behind backing, is not utilized. For tufted carpets the thickness of the backing is a substantial factor in how much of the pile fiber is used effectively. The lubricated sheets of this invention can be prepared in a form which makes possible a substantial saving and greater efi'iciency of use of pile fibers, which can be translated by the carpet manufacturer into either a more luxurious carpet at the same cost, or alternatively, a less expensive carpet of the same level of performance.

The use of nonwoven fabrics as described in the present invention has a substantial and important cost advantage over the use of conventional woven fabrics. In addition, with most tightly woven fabrics, the tufting operation by which the tuft piles are inserted into the backing, will cause damage to the yarns of the backing. On the other hand, most loosely woven structures, while not damaged by tufing, are not as strong and Will not serve as satisfactorily.

The continuous filament nonwoven structures which are employed in the process of the present invention overcome these difficulties and provide backing materials with a very high level of fabric strength. The nonwoven nature of the backing material, and the random disposition and configuration of the fibrous elements insure that there will be no close alignment of fiber elements. Accordingly, during the tufting operation, the opportunity for damage by tufting needles is substantially reduced. An additional advantage of the nonwoven fabric of this invention over woven fabrics is that they permit uniform tufting at high stitch counts, e.g. 12-15 stitches per inch (4.7-5.9 per cm.)

The nonwoven fabrics of this invention also have important functional advantages over conventional nonwoven fabrics. Thus it has been found that nonwoven fabrics now commercially available, in particular the resin-bonded staple-fiber nonwoven fabrics, haveunacceptable strength after tufting. In all cases, the tufting needles tear holes in the fabric even when properly lubricated according to this invention, rather than slipping through with relatively little damage as in the case of the nonwoven fabrics of this invention.

Any fabric to be used as a primary carpet backing must be of such a nature that it is not seriously weakened in its tensile and tear strentgh properties during tufting. A woven fabric tends to deflect the needles into spaces between yarns, while a nonwoven fabric must be composed of individual fibrous elements having sufiicient mobility and tenacity to be displaced Without rupturing while still retaining sufiicient strentgh to undergo processing in the form of retufting and beck dyeing. In order to possess sufiicient strength, the nonwoven structures employed in the process of this invention must be bonded, but too heavy bonding brings about immobilization of the filaments and leads to excessive breakage of filaments during tufting. However, even a properly bonded sheet must be treated with a polar lubricant such as listed heretofore to apply a layer of the lubricant on the surface of the filaments and thereby provide the full level of filament mobility required for tufting without excessive damage due to breaking of filaments.

The polar lubricants which are effective for use on the nonwoven sheets of this invention reduce web-friction forces during tufting, which includes both fiber-to-fiber and fiber-to-needle friction, and are inert to the filaments, that is, they do not cause any significant loss in filament strength. Preferably, the lubricants have the ability to wet the filaments. Other desirable characteristics in the preferred lubricants are a low level of absorption into the filaments and poor solvent action on the stabilizers used in the polymeric filaments. The above listed examples of lubricants are all useful in this invention although they differ considerably in their effectiveness in reducing friction forces. This is exemplified by the fact that the polysiloxane lubricants are effective at a concentration as low as 0.3% on the surface of the filaments, while the other lubricants require a concentration of 1 to 2%. Moreover, even at the optimum lubricant levels, the polysiloxanes are more effective lubricants based on the grab-tensile strengths of the tufted sheets. For these reasons the polysiloxanes are the preferred lubricants.

The lubricants listed above also differ in the amount which is absorbed into the filaments of the bonded nonwoven sheets. Thus, in accelerated absorption tests with a self-bonded nonwoven sheet of oriented polypropylene filaments, wherein sheets containing 4% lubricant are heated for various periods of time at 100 C., the absorption of methyl hydrogen polysiloxane leveled off at 0.4-0.5 and that of dimethyl polysiloxane at 0.70.8%, respectively, after minutes. On the other hand a maximum absorption of about 3% was obtained with 2-ethylhexyl sebacate and dioctyl sebacate after about 5 minutes and with coconut oil and acetyl tri-Z-ethylhexyl citrate after about 10 minutes. These results are consistent with room temperature storage studies in which the level of absorbed polysiloxanes reached about 0.2% after 8 weeks, while the level of absorption of coconut oil and Z-ethylhexyl silicate reached 1% in 1 week and 2% in 8 weeks, and the level of absorption of 2-ethylhexyl sebacate and dioctyl sebacate reached 2% in 3 to 4 days and 3% in 3 weeks. In a separate test, 0.16% of methyl hydrogen polysiloxane was absorbed after storage for 6 months.

It has been found that tufting response is independent of the amount of polar lubricant absorbed by the filaments and likewise is not affected by the heat treatment used in the accelerated test. It is, however, dependent on the amount of lubricant on the surface of the filaments, and accordingly, in order to guarantee tuftability after several months storage, a sufiicient quantity of lubricant must be used to provide both for that which is absorbed and that which is required on the filament surfaces. For example with coconut oil which requires about 2% on the surface to be effective and which is absorbed to an extent of about 3%, about 5% would be required initially to guarantee tuftability several months later. With the referred polysiloxanes, which show a lower absorption and also effective tufting at lower surface concentration, only about 1% is required for assured good tuftability after several months storage.

Absorption of the polar lubricants used in this invention does not appear to affect significantly the bond strengths or the filament properties by filament plasticization. While the lubricant may weaken the bonds slightly, the major role of the lubricant is the reduction in friction by that portion of the lubricant which remains on the filament surfaces.

A number of the lubricants, e.g. coconut oil and 2-ethylhexyl silicate, which are readily absorbed by the bonded filaments also tend to be good solvents for common stabilizers such as dilauryl thiodipropionate and 2-hydroxy-4- n-octyloxybenzophenone used in polypropylene. It is found that the stabilizers rapidly reach an equilibrium with the lubricant. For example with coconut oil, the stabilizers appear to be nearly in the lubricant. The amount of stabilizer left below the surface of the filament is then proportional to the amount of lubricant absorbed. Since coconut oil is readily lost from the backing when the tufted carpet is passed through the dye beck, at least that stabilizer present in the coconut oil on the surface of the filaments is removed during the dyeing operation. The polysiloxanes, on the other hand, are poor solvents for the stabilizers, or at least they do not readily extract them from the filaments. As a result, the polysiloxanes have little effect on stabilizer losses and accordingly the stabilizers remain in the filament matrix where they are effective. This property of the polysiloxanes, coupled with their low level of absorption into thhe filaments, provides another reason for preferring the polysiloxanes for the lubricated sheets of this invention. If desired, an amineor acid-modified polysiloxane may be incorporated into the preferred polysiloxane lubricants to make the lubricated nonwoven sheets of this invention receptive to acidic or basic dyes.

The operable lubricants in this invention can be applied to the bonded nonwoven sheet by any of the methods known in the art for the application of textile finishes. Thus, application by spraying, padding, roll coating, etc. can be used. The lubricant composition may be in the form of an aqueous dispersion or solution in an organic medium, or it may be applied without a diluent. Lubricants with a viscosity in the range of 1 to 200 centistokes are well-adapted to application by gravure coating techniques. If an organic medium is used, it should be one which has no solvating or plasticizing effect on the polymeric filaments.

Briefly stated, the aforementioned primary carpet backings are lubricated, bonded sheets of highly crystalline continuous filaments of the classes defined above, disposed in random fashion throughout the sheet. The filaments are separate and independent from each other, except for being bonded at a multiplicity of bond points.

The continuous-filament bonded nonwoven sheets employed in the practice of the present invention provide maximum strength at minimum weight in addition to other desirable characteristics. In one embodiment of this invention, the bonds in such sheets derive from the fiber elements themselves and occur at crossover points between fibers. The matrix filaments in the bonded sheet possess a birefringence that is at least 40% of the calculated maximum birefringence of fibers of the polymer constituting the filaments.

The self-bonded sheets used for primary carpet backings in accordance with this first embodiment of the invention are bonded at a multiplicity of intersection points and the required bond structure in the sheets is characterized by an edge bond count of between 30 and 80 bonds per hundred filaments. These sheets and their preparation are described in copending Levy application, Ser. No. 305,875, filed Aug. 30, 1963, now Patent No. 3,276,944.

The preferred method for making this embodiment of the primary backings is by exposing throughout its three dimensions, a nonwoven Web with the aforementioned geometry and comprising continuous, isota'ctic polypropylene filaments having a birefringence of between about 0.016 and 0.04 and a crystallinity index of at least 40%, to saturated steam at a temperature in the range of about 45 C. below up to the crystalline melting point of the polymer while restraining the Web with a force sufficient to prevent filament shrinkage of more than Temperature variation throughout the web is maintained within a 0.5 C. range. The heat-up rate and the selected exposure temperature must be suflicient to self-bond the filaments at a plurality of spaced intersection points to provide a sheet having a strip tensile (ASTM D-39 using a specimen 2.0 x 2.5 cm.) of at least 3 lb./in.//oz./yd. (l6 g./cm.//g./m. While preventing a drop in filament birefringence of greater than 50%. Also the bonding temperature must be below that which would produce an edge bond count above 80 or a birefringence lower than 40% of the calculated maximum birefringence of the filament. By this method, no loss of fiber identify occurs.

Maximum birefringence is determined in accordance with H. M. Morgans Correlation of Molecular Orientation Measurements in Fibers by Optical Birefringencev and Pulse Velocity Methods, Textile Research Journal, 866, October 1962. The maximum birefringence for filaments of isotactic polypropylene is 0.04 and for linear polyethylene is 0.06.

In addition to the filaments heretofore described, up to by weight of the total Web may comprise other filaments which will not self-bond under the bonding conditions employed. These other filaments may be termed inert filaments and may be made of glass, metal or other inorganic or organic filaments. There may also be present small amounts of adjuvants such as fillers, delusterants, pigments, coloring materials, stabilizers and the like. For example, ultraviolet light stabilizers may be incorporated into the polymer before spinning into filaments.

The range of temperature for self-bonding filaments is relatively narrow and lies in the range of between 45 below the crystalline melting point of the polymer up to the crystalline melting point. The crystalline melting point can be determined by the method outlined in Preparative Methods of Polymer Chemistry by W. R. Sorensen and T. W. Cam bell, Interscience Publishers, Inc., 1961, pp. 44-47. In applying the procedure to fibers it is necessary to immobilize the fibers on the slide by securing their ends with a suitable heat-resistant adhesive or tape. The crystalline melting point may not be exceeded, and in some instances even lower temperatures may be too high for the process because of too rapid a heat-up rate.

By self-bonded is meant that the highly crystalline and oriented filaments are fused to each other at crossover or intersection points. No foreign material is present to achieve bonding. Filament and web geometry of the bonded sheet is substantially the same as the unbonded web except for the bonds. In some cases, flattening of filaments occurs because of the restraining forces employed.

Microscopic studies show that the major cross-sectional dimension of each filament at the bond site is less than twice that of the unbonded filament segments adjacent the bond sites. It is also noted that the bonds are weaker than the filaments as evidenced by the fact that exertion of a force tending to disrupt the sheet, as in tufting, will fracture bonds before breaking filament.

The bonded Webs will exhibit an edge bond count (EBC) of between 30 and bonds per hundred filaments. Lower levels of bonding result in sheet materials having relatively low tensile strength. Exceeding an EBC of 80 results in excessive filament breakage during tufting. Sheet tear properties are also deleteriously aifected at high BBC. Low tear strength is also obtained where filament birefringence is less than about 40% of maximum birefringence. By achieving high filament orientation along .with the indicated degree of bonding, the unique result of both high tear and tensile strength is obtained.

The bonded sheet materials will contain self-bonds which are distributed throughout the textile product both randomly and uniformly. However, it should be realized that certain modifications may be made either during the bonding process or thereafter to modify this distribution to some extent.

The method employed for determining the average edge bond count of bonded samples is described as follows:

The number of bonds per filaments, as counted on the edge face of a bonded web is used as a measure of the amount of self-bonding. This count is based on the probability that the appearance of a bond at an edge face is dependent upon (1) the number of bonds, (2) the size of the bond, and (3) the distribution of these bonds.

The edge bond count measurements are made on samples taken from a representative 6-inch (15 cm.) square test piece of bonded sheet. Four samples are taken from the test piece, one from near each of the four corners in such a fashion that the cross sections to be counted later will come from edges parallel to the four edges of test piece. These samples are fastened in a frame and embedded in an epoxy resin which is then polymerized. The embedded specimens are trimmed so that at least a 0.25 in. (0.64 cm.) cross-section of the sheet is exposed for microtoming. These samples are microtorned transversely to the face of the sheet at a thickness of about 6 microns, and the resulting sections are deposited in immersion oil on the micrometer stage of a polarizing Projectina N0. 4014. This apparatus is a microscope (distributed by Hudson Automatic Machine and Tool Company, 137-139 38th St., Union City, N.J.), which projects a view of the section onto a screen from which the filaments and bonds are counted. A 10 eyepiece and a 20X objective lens are used. The polarizer and an RI red filter are used to improve filament definition. In the projected view of the section of the sheet, the filaments will appear in various shapes depending on the angle at which they were cut by the microtome. Thus all the variations from a transverse cut perpendicular to the filament axis to a longitudinal cut parallel to the filament axis may be present. Each filament in the projected view is counted once. A bond occurs and is counted whenever there is no complete separation between any two filaments. Thus, while a filament is counted only once, that filament may participate in from 0 to 5 or more bonds depending on the number of other filaments it contacts. For example, if a filament contacts two other filaments, the filament count is 3 and the bond count is 2. If the other two filaments also contact each other, the filament count is 3 and the bond count is 3. At least one full 0.25 in. (0.64 cm.) slice is counted and not less than 200 filaments from each embedded sample. The number of bonds per 100 filaments is averaged from the four samples and reported as the average edge bond count.

In the examples, the strip tensile strength of the sheet was measured in lb./in.//oz./yd. (g./cm.//g./m. according to the method of ASTM D1682, except for the fact that sample width is 0.5 inch (1.27 cm.) the distance between the jaws on the tensile machine is inches (12.7 cm.) and the jaw speed is 100% per minute. The tongue tear measurement was in accordance with ASTM D39 except that specimens were 2 in. x 2.4 in. (5 cm. x 6.4 cm.).

A measure of the crystallinity index of th synthetic organic polymeric filaments can be obtained by means of X-ray diffraction techniques.

In order to determine the birefringence of filaments within a bonded sheet structure, a thin layer of the sheet is obtained either by careful delamination or by sectioning with a razor blade. This is necessary since light must pass through the filament being tested without interference from other filaments. The birefringence of round filaments may be determined using a polarizing microscope with a Berek compensator known to the art and referred to in detail in the aforementioned Levy application. Measurements should be made on at least ten filaments and the results averaged.

In another embodiment of bonded nonwoven sheets which can be used in the lubricated products of this invention, the bonds required for adequate filament mobility during the tufting operation are characterized as follows, considering only those bonds which have a strength greater than 0.1 gram: (1) the average bond strength is at least 0.9 gram and less than the filament-breaking strength; (2) the distribution of bond strengths is such that th variance (a is greater than 4 and (3) the number of bonds is such that the product (NE) of the number of bonds per cubic centimeter (N and the average bond strength is greater than 5x10 g./cm. and this product divided by the filament-breaking strength is less than 9 10' /cm. T-he filament-breaking strength referred to above is the strength in the bonded nonwoven sheet. Variance, as used herein, has its accepted meaning in statistical analysis and is defined as follows:

where 0' is the variance g is the arithmetic mean of the bond strengths s is the measured value of the individual bond strengths,

and

m is the number of measurements.

It has bee-n found that nonwoven sheets which have the above-defined bond characteristics and which have been properly lubricated, provided tufted carpets with a good bond strengths and bond concentrations to give acceptable products. A narrow distribution product, such as the self-bonded sheets previously described, necessitate very narrow limits on the number of bonds and precise control of the bonding conditions to obtain a good product.

The nonwoven sheets of this embodiment of the invention are composed of matrix filaments of hydrocarbon polymers of the same types as used in the self-bonded structures. However, instead of depending solely on selfbonds, adhesive bonds, that is, bonds between two different materials, can also be present and satisfactory sheets are obtained if the bond strength and concentration come within the structural limitations defined above.

A particularly preferred sheet material for use in this embodiment of the invention is produced from nonwoven webs of continuous filaments of oriented isotactic polyproplylene as the matrix filaments and unoriented or loworiented isotactic polypropllene filaments as the binder material. By virtue of the lower degree of orientation in the binder filaments, they have a lower softening point than the matrix filaments. By choosing the proper bonding temperature, bonds comprising self-bonds between the matrix filaments, self-bonds between the binder filaments and inter-bonds between the matrix and binder filaments can be produced. Since these can have different bond strengths, the required variance in bond-strength distribution can be readily obtained. It is necessary when practicing this method, however, to operate the bonding step at a sufiiciently high temperature to obtain some degree of self-bonding between the matrix filaments. This can be readily obtained since the softening point of the loworiented binder filaments is usually only about 5l0 C. below that of the more highly oriented filaments.

The binder filaments can be incorporated into the nonwoven web as separate low-oriented filaments or as loworiented segments of mixed-orientation filaments. Either of these methods can readily be adapted for use in the aforementioned process of British Patent 932,482 for the production of continuous-filament nonwoven sheets. Separate binders and matrix filaments can be produced by using two separate spinning and drawing machines and combining the filaments prior to or during web laydown. They can also be produced by splitting the thread line from the spinneret so that a part bypasses the drawing operation. Another method involves the use of a spinneret with varying capillary geometry which produces filaments with varying responses to the drawing operation. Nonwoven Webs of filaments with segments having different levels of orientation can be produced by pulsing the throughput of polymer going to the drawing operation, by pulsing the draw ratio in the drawing operation, or by variation of the drawing temperature. This latter method can be carried out by passing the filaments over a fluted feed roll in the drawing step. It has been found that these various techniques produce satisfactory mixedorientation webs for use in producing the nonwoven sheets of this invention.

The oriented polypropylene matrix filaments in the unbonded nonwoven web will normally have a birefringence in the range of 0.020 to 0.040, while that of the binder filaments will be in the range of from less than 0.01 to about 0.03 and will always be less than that of the matrix filaments.

As indicated above, it is necessary to carry out the bonding of the nonwoven web under controlled conditions so that some degree of self-bonding between the matrix filaments will be obtained. The bonding procedure described previously for self-bonding of nonwoven webs of oriented polypropylene filaments is applicable to the bonding of these nonwoven webs of mixed orientation filaments. Thus the nonwoven web is held under restraint while being exposed to a saturated steam atmosphere at the pressure required to obtain the desired bonding temperature. While controlled bonding conditions are required to obtain the required bond strength, distribution and concentration, the bonding conditions are much less critical and it is easier to produce acceptable product than with the nonwoven webs which are bonded solely by self-bonds between the matrix filaments. While selfbonding of oriented filaments requires temperature control within a range of about C. and preferably within 0.1" C., the bonding of mixed-orientation webs can be carried out within a range of about 3 C. and preferably within a range of 1" C. The actual bonding temperature used with the mixed-orientation webs is also lower, thus it is easier to maintain the desired birefringence in the matrix filaments, which is indicative of good filament tenacity.

A method which can be used to measure the average bond strength in this embodiment of bonded nonwoven sheets used in this invention is described below. A sample of the bonded nonwoven sheet (2 in. x 0.125 in.) (5 cm. x 0.32 cm.) is delaminated into as many layers as can be obtained without distortion of the individual strips. The number of layers obtained will vary with the product being tested but will usually be between 3 and 10. The purpose of delaminating and using narrow samples is to obtain layers having a limited but representative number of bonds so that in the subsequent tensile test, individual bond breakage can be followed and the likelihood of multiple bonds breaking simultaneously is minimized. Each of the delaminated layers is pulled apart in an Instron Tensile tester using a l-in. (2.5 cm.) jaw separation and a strain rate of 0.02 in. (0.05 cm.) per minute. The instrument is calibrated to 40 grams full scale, thus permitting readings down to 0.1 gram. Bonds having strengths less than 0.1 gram are not measured. On the stress-strain curve so obtained, the drops in load, after the maximum stress (F is reached, are attributed to breakage of individual bonds. The magnitudes of these drops, which correspond to individual bond strengths, and their number are determined.

As a delaminated layer is elongated, the resultant stress (F) is distributed over the bonds supporting the stress in the strip. At any section across the layer the stress (F) will be distributed among the bonds supporting stress within that section. The stress potential of such section will be determined by the product of the number of bonds (N supporting the stress and their average strength When the force on the layer exceeds the value of N for the weakest section of the layer, it will begin to fail at that point, and bonds in that section will begin to break. At higher elongations, the layer is held together by a few fibers and on continued elongation, bonds are broken in sections further back and outside the original section of the bond breakage. This expanding area of bond breakage is not definable and some basis is needed to limit the bond-strength measurement to some small finite section which can be measured. The proper amount of elongation is determined from the maximum stress recorded (F which is equal to N 'S for the section of the layer which breaks. Accordingly,- the layer is elongated until the value of NS and F give the required agreement.

The section of bond breakage is determined by taking photomicrographs of the delaminated layers before and after the bond-breaking test, comparing the same and measuring the area of disruption. This is the area that does not remain intact as seen from a comparison of the before and after photomicrographs. The thickness of the original sample can be readily measured by known methods, for example, with an Ames gauge. From the area of bond breakage and the thickness of the original nonwoven sheet sample, the total volume, i.e., the section, of the sample in which the bond break-age occurred can be calculated.

In addition to the bonds in the individual delaminated layers, it is necessary to obtain a measure of the bonds broken in obtaining the delaminated layers. A measure of these bonds is obtained by delaminating the samples on the Instron Tensile tester at a strain rate of 0.05 in./ min. (0.\127 cm./min.) and noting the number and strength of the bonds broken over a volume equal to that affected in the above tensile test. The average bond strength, number of bonds, and the variance of the bondstrength distribution are calculated from the bond strengths measured on all the delaminated layers as well as those measured during delamination. From the area of bond breakage, the thickness of the sample, and the number of bonds which have been broken, the number of bonds per cubic centimeter can be calculated.

The operation of the present invention can be more clearly comprehended in examples which illustrate preferred practice. The following examples give such illustrations, however, without intending or suggesting any limitation to the scope of the operations described.

Examples I through V below, illustrate one type of bonded sheet that can be lubricated in accordance with the present invention. These sheets are suitable for use as a primary carpet backing for tufted carpet after application of a suitable lubricant.

Example I Isotactic polpropylene (MFR 108) having a melt index of 4.5, and containing 0.2% by Weight of a tan-coloring pigment is screw extruded at a maximum temperature of 290 C. and metered at 1 8 g./min. through a 0.25 in. (0.64 cm.) layersand filter bed and a 2 in. (5 cm.) spinneret of 30 holes, each 0.015 x 0.020 in. (0.038 x 0.051 cm.) in size. The pack block is held at 275 C. and the spinneret temperature is controlled at 272 C.

Directly below the spinneret, the filaments are drawn 3.8x to a high level of orientation using draw rolls.

The bundle of filaments is quenched in a 3 in. (7.6 cm.) orifice quench chimney using air flow of 700 ft./min. (210 m./min.). The top of the quench chimney butts against the bottom of the spinning pack to minimize the effect of air flow on the spinneret temperature. Below the quench chimney, the filaments are charged with a corona discharge device. A negative corona is formed from a four point source at a distance of 0.63 in. (1.6 cm.) from a 1.25 in. (3.2 cm.) O.D. bar rotating at 10 rpm. The threadline makes light contact to the target bar, the centerline of which is 8 in. (20 cm.) above the entrance to the forwarding jet. A negative voltage of 10 kv. ,ua.) is applied to the corona points.

The forwarding air jet impels the filaments toward a traversing-table receiver, to form a nonwoven web of randomly distributed filaments. Filament throughput is 18 g./min.

Filament properties are as follows:

Denier (0.87 tex) 7.8 Tenacity g.p.d 4.6 Elongation "percent" 72 Modulus g.p.d 43

The web formed in this manner is coherent, even without bonding. The filaments are randomly distributed. Unit weight is 3.6 oz./yd. (122 g./m. The appearance of the web is uniform and is essentially free from filament aggregates. The fabric is bonded by the application of saturated steam at 97 p.s.i.g. (6.8 kg./cm. while the fabric is compressed between a canvas cloth and a 16 mesh wire screen. The tensile strength is 7.7 lb./in.//oz./ yd. (41 g./cm.//g./m. and the tongue tear strength is 8.5 lb.//oz./yd. (114 g.//g./m. The filaments in the web exhibit high crystallinity and a birefringence of at least 0.016.

Example II In a similar procedure, isotactic polypropylene (MFR 14.2 and melt index of 5.9) is spun at 275 C. through a sand pack and a 30 hole, 0.015 x 0.075 in. (0.038. x 0.190 cm.) spinneret at 18 g./min.

The polymer contains 0.1% of a dark-brown coloring material. Air at 12 C. is made to quench the filaments in a 3 in. (7.6 cm.) orifice tube, at linear feet per minute (38 m./min.).

11 Following the quench, the filaments are roll drawn 5.1 Filament properties are:

Tenacity g.p.d 4.5 Elongation percent 63 Denier (0.80 tex) 7.2 Modulus g.p.d 48.2

After drawing, the filaments are charged and forwarded in a manner similar to that already described.

The filaments are deposited in random fashion on a belt receiver, operating continuously at a speed of 0.285 yd./min. (0.261 m./min.). The web width is 28 in. (71 cm.) before trimming. Following deposition, the web is pressed between cold rolls to consolidate the structure, and then the web is self-bonded by the application of saturated steam. It has an edge bond count within the range of 30-80. The filaments in the web exhibit high crystallinity and a birefringence of at least 0.016.

Example III A web is made in a similar manner as in Example 11 above from a polymer containing 0.05% of a dark brown pigment.

Filament properties:

Tenacity g.p.d 4.03 Elongation percent 130 Denier (0.80 tex) 7.2 Modulus g.p.d 40.0

The web is bonded by steam at 84 p.s.i.g. (5.9 kg./cm. to yield a sheet with an edge bond count of 69. Sheet properties are:

A nonwoven web of isotactic polypropylene filament is prepared as follows: Polypropylene (MFR 9.6) filaments are spun from a 30-hole spinneret at a rate of 18 g./min. total. Each spinneret hole is 0.020 in. (0.051 cm.) in diameter and the spinneret is at 250 C. The filaments are drawn 4 after spinning. The filaments have a denier of 8.2 (0.91 tex), a tenacity of 4.4 grams/denier, and elongation of 107%, a modulus of 30.5 grams/denier, a crystallinity index of 43%, and a birefringence of 0.031.

The filaments are fed to a heated feed roll operating at a surface temperature of 115 C. and then around the roll advancing the yarn by means of an idler roll canted with respect to the heated roll. A total of 5 wraps are used on the heated feed roll, which is operated with a surface speed of 203 yd./min. (18.6 m./min.). The yarn leaving the heated feed roll is then passed 5 wraps around an idler roll/ draw roll system operating cold with a surface speed of 800 yd./min. (731 rn./min.). The drawn filaments are then charged with a corona discharge device, passed into a draw jet for separation and subsequently randomly deposited on a reciprocating table. The web is bonded by passing it at a speed of yd./min. (9 m./min.) while under restraint between one porous metal plate and one solid metal plate, each faced with cloth, through a steam chamber for a distance of 37 inches (94 cm.). The steam chamber contains saturated steam held at 70.5 p.s.i.g. (4.95 kg./cm. on the porous plate side and 72 p.s.i.g. (5.05 kg./cm. on the solid plate side (corresponding to a saturated steam temperature of 158 C. and 158.7 C. respectively). The difference in pressure on the two plates serves to restrain the web and filaments against shrinkage during bonding.

A very tough nonwoven bonded sheet suitable for use as a primary carpet backing is obtained. Its physical properties and structural parameters are given as follows:

Unit weight 2.8 oz./yd. g./m. Tensile strength 8.2 lb./in.//oz./yd. (43 g./

cm.//g./m. Elongation 40 percent. Tongue tear 6.4 lb.//oz./yd. (86 g.//g./

111. Edge bond count 60 bonds per filaments. Crystallinity index 52 percent. Birefringence 0.028.

Example V A nonwoven web is prepared from polypropylene continuous filaments by the same procedure as that described in Example IV, with the exception of the draw ratio. In this example the filaments are drawn 1.36 after spinning from the 9.6 MFR polymer to give a random fibrous web of 3.5 denier (0.4 tex) filaments. The filaments have a tenacity of 2.1 grams/denier, an elongation of 355%, a modulus of 14.5 grams/denier, a birefringence of 0.025, and a crystallinity index of 44%. This web is bonded by passing it at a speed of 10 yd./min. (9 m./min.) through a steam chamber 3 feet (0.91 m.) long containing saturated steam at 53 p.s.i.g. (on the porous plate side) and 54 p.s.i.g (on the solid plate side) (corresponding to a temperature of 149.3 C. and 149.8 C. respectively). Its properties are listed below:

Unit weight 3.5 oz./yd. (ll9 g./m. Tensile strength (ASTM D'l682) 6.4 lb./in.//oz./yd. (34 g./

cm.//g./m. Elongation 54 percent. Tongue tear (ASTM D-39) 4.6 lb.//oz./yd. (62 g.//g./

m. Edge bond count 61 bonds per l00 filaments. Crystallinity index 57 percent. Birefringence 0.025.

Example VI A polypropylene nonwoven sheet prepared as described in Example IH above is suitable for use as a primary rug backing. Prior to tufting, the sheet is treated with a polysiloxane lubricant, applied in the form of a 4% aqueous dispersion with also contains 0.4% of a surface active agent (sodium alkylarylsulfonate). The excess lubricant dispersion is squeezed out through a nip roll and the wet sheet is then dried prior to the tufting. The lubricant take up is about 3% based on the dry sheet weight.

The lubricated sheet is tufted using a standard commercial tufting machine with conventional needles having a diameter of 0.140 in. (0.356 cm.) operating at a spacing of 7 stitches per inch (2.8 per cm.) with tuft rows at 0.188 in. (0.48 cm.) separation. Styling effects can be obtained by varying the tuft height and linearity of the tuft rows.

The tuft height is 0.44 in. (1.11 cm.). The tufting yarn used is a nylon carpet yarn. In similar experiments using the same type of backing, rayon, cotton, wool and acrylic fiber tufting yarns are employed.

After tufting, the carpet is dyed by conventional means using a dye beck for broadloom carpets. Following this the back of the tufted rug is latexed and dried to hold the tufts in place.

Physical properties of the carpet of this experiment are given in Table I, which also shows the properties of a conventional, jute-backed carpet.

14 propylene nonwoven sheets, prepared and self-bonded as hereinbefore described, and having an average edge Nonwoven bond count of from 65-70 are treated with a variety of P p py lubricants as indicated in Table II below. The sheets are tufted within two days after lubricating. The X-D grab 0.011 in. (0.028 tensile strengths of the tufted samples are then deter- (146 mined. The results are reported in Table II as adjusted l ggrab tensile, which represents the relative performance i jf of these samples compared, on-a percentage basis, with the grab tensile of a similar tufted sheet lubricated with a mixture of methyl hydrogen polysiloxane and dimethyl polysiloxane. The absolute value for such a control sheet,

having a unit Weight of 4 0z./yd. (136 g./m. is about TABLE I .lute

0111.). 10 oz./yd. g./m. 112 lb. (51 k 26 lb. (12 kg.) 53 V Primary Backing Material pet tensile (grab, XD arpet tongue tear (MD 1 XD is cross-machine direction. 2 MD is machine direction.

Backing thickness Unit weight of baeking Car Dimensional Stabilit Shrinkage after wet cleaning. 3.5%

provides improved strength and great increase in dimen- 3 Percent change in length on increasing ambient relative humidity from RH to 90% RH at 65 F.

As Table I shows, the carpet backing of this invention sional stability. Such stability is important pet, and is especially desirable in wall-to to eliminate wrinkling and slack caused 13 humidity.

t can also Adjusted Grab Tensile ican operable polar lubricants Ilhbricant Pickup 0 62089 68074 b 0 99098 888 1 m 1 1 G as en t S T M 00040 43290 LZZLL Lubricant Pickup 7 g a predominant amount or greater) of operable lubr hown as operable lubricants in this example.

Combinations of the above and other mixtures containin (e.g., 80% tion, polybe used as s in Table III.

TABLE II Lubricant perable Run No.

Example VII To demonstrate the essential function of the o polar lubricants in the process of this inven Boric Acid pplied as aqueous dispersions of solutions. Lubricants TABLE III PENP 5 11-12 are a pplied with no diluent. y sheet weight.

aqueous dispersion containing 0.4% sodium alkylarylsulionate.

plied as 4% [Lubricant Composition (percent) DEAF 3 l Lubricants in Runs 2-4 in Runs 5-10 are a 2 Based on dr a AP 4 Applied as dispersion containing polyoxyethylene nonyl phenol as wetting agent.

Run No.

1 All lubricants applied from aqueous systems.

2 Potassium n-octyl phosphate.

3 Diethanol amine salt of Cs-Ciz alkyl hydrogen phosphates; alkyl groups present in ratio corresponding to 60/30/10 mixture of CB/Cio/Ci: alkanols.

4 Potassium oleate.

5 Polyoxyethylene nonyl phenol.

6 /50 copolymer of ethylene oxide/propylene oxide.

7 Based on dry sheet weight.

1 5 Example VIII A broadloom carpet prepared as in Example VI is further reinforced with an unlubricated bonded sheet described in Example V above as a secondary backing. The secondary backing is adhered to the primary backing by means of latex which is applied to the back of the carpet and/or to the secondary backing, after which the two are pressed together, and the whole carpet is dried in a continuous process in an oven drier.

The carpet thus prepared is tested, and the physical properties are compared with another carpet which differs in that the secondary backing is woven jute, rather than the synthetic nonwoven prescribed in the present invention. Comparison of physical properties is given in Table IV below.

TABLE IV Primary backing Nonwoven Poly- Nenwoven Polypropylene. propylene. Secondary backing Jute- Do. Backing thickness (total). 0.059 in. (0.150 0.020 in. (0.051

cm.). cm.). Unit weight of backing (total). 13 ox.)/yd. (440 g./ 6 oxyd. (203 g./

in In Carpet tensile (Grab, XD) 2751b. (125 kg.) 185 lb. (84 kg.). Carpet Tear (Tongue, MD) 55 lb. (25 kg.) 30 lb. (14 kg.). Dimensional stability (Percent 0.1 0.1.

change). Shrinkage after wet cleaning 1.0

(Percent).

It is apparent that while both carpet constructions offer more than adequate strength, the carpet with both backing materials made of synthetic nonwoven sheets is superior in resistance t shrinkage.

Example IX A randomly laid nonwoven web with a unit weight of 4.4 oz./yd. (149 g./m. is prepared from linear polyethylene having a melt flow rate of 14. The filaments have a denier of 7.5 (0.83 tex) and a tenacity of 3.4 grams/ denier. The sheet is steam bonded, lubricated, and tufted. Table V below gives the team bonding conditions, identification of lubricants and properties after tufting. The birefringence of the filaments before and after bonding is 0.048 and 0.042, respectively.

TABLE V Web bonded at 28 p.s.i.g. (132.9 29 p.s.i.g. (133.6

O.) (1.97 kg./ 0.) (2.04 kg./ cm. cmfl). Edge bond count Lubricant: A mixture of 4.1% L. 5.2%.

methyl hydrogen polysiloxane and dimethyl polysiloxane. Properties after tulting: Tuft- 138 lb. (63 kg.) 127 lb. (58 kg.)

edgrab-tensi1e. MD MD 132 lb. (60 kg.) 135 lb. (61 kg.) XD XD). Elongation at maximum lead. 104% (MD) 91% (MD). 98% (XD) 96% (XD). Tongue tear (MD) 31 lb. (14 kg.)-- 37 lb. (17 kg.).

Applied as 4% aqueous dispersion containing 0.4% sodium alkylarylsulfonate.

Example X A web is prepared from isotactic polypropylene having 4% atactic content (MFR 11.5) following the general procedure of Example IV with the following variations: The polymer is spun through a spinneret having 0.015 in. (0.038 cm.) holes and the spinneret is at 223 C. The filaments (8 d.p.f.; 0.9 tex) are drawn 4.2x, charged and received as a random web on a moving belt. The filaments have a tenacity of 4.0 g.p.d. and a birefringence of 0.030. The web, having a unit weight of 4.3 oz./yd. (146 g./m. is bonded at 164.2 C.

The bonded sheet is 0.017 in. (0. 043 cm.) thick and has an average edge bond count of 70, a birefrigence of 0.026, and an average uniformity ratio of 1.07. The

16 r sheet has a tensile strength of 6.0/7.1 lb./in.//oz./yd. (32/37 g./cm.//g./m. (MD/XD) and a tongue tear of 6.8/5.8 lb.//oz./yd. (91/78 g.//g./m. (MD/XD).

The bonded sheet is lubricated with a mixture of methyl hydrogen polysiloxane and dimethyl polysiloxane and tufted with pile yarn on a commercial tufting machine. Few filaments in the sheet break during tufting. The carpet grab tensile is 198 pounds kg.) and the carpet tongue tear is 59 pounds (27 kg).

Example XI A nonwoven web of 14% low-oriented and 86% highoriented isotactic ploypropylene filaments is prepared as follows: polypropylene (melt flow rate 12) is spun through a 30-hole spinneret at a rate of 18 g./min. total and through a S-hole spinneret at a rate of 3 g./r'nin. total. Each spinneret hole for both spinnerets is 0.015 in. (0.038 cm.) in diameter. The temperature of the 30-hole spinneret is 242 C. and the 5-hole spinneret, 220 C. The filaments from the 30-hole spinneret are led around a heated feed rool operating with a surface temperature of 118 C., and advanced by means of an idler roll canted with respect to the heated roll. A total of 5 wraps is used on the heated feed roll, which is operated with a surface speed of 243 yd./min. (222 m./min.). The filaments leaving the heated feed roll are then passed 5 wraps around an idler roll/draw system operating cold with a surface speed of 858 yd./min. (785 m./min.). These high-oriented filaments are thus drawn 3.5x, are 7.48 denier (0.83 tex) per filament and have a tenacity of 4.03 g.p.d. The filaments from the 5-hole spinneret are led to a heated roll operating with a surface temperature of C. and a surface speed of 703 yd./min. (642 m./min.). The filaments are in contact with the heated roll for 180. The filaments leaving the heated roll are then passed to a draw roll operating cold with a surface speed of 852 yd./min. (779 m./min.). The filaments are in contact with the draw roll for 180. These low-oriented filaments are thus drawn 1.21 are 7.73 denier (0.86 tex) per filament and have a tenacity of 1.62 g.p.d. The filaments from both spinnerets meet and are guided so the low-oriented filaments are uniformly dispersed throughout the high-oriented filaments. The filaments are then electrostatically charged with a corona discharge device, passed into a draw jet and subsequently deposited on a moving belt to form a nonwoven web of randomly distributed continuous filaments.

The filamentary web, unit weight 3.84 oz./yd. g./m. is bonded by passing it at a speed of 10 yd./min. (9 m./min.) while under restraint between one porous metal plate and one solid plate, each faced with cloth, for a distance of 37 in. (94 cm.) through a steam chamber in which saturated steam is maintained at a pressure of 75 p.s.i.a. (5.3 kg./cm. The restraint on the web is 0.75 1b./in. //0z./yd. (1.56 g./cm. //g./m. The bonded sheet is lubricated by immersing in a 4% aqueous dispersion of a mixture of methyl hydrogen polysiloxane and dimethyl polysiloxane which also contains 0.4% of a surface active agent (sodium alkylarylsulfonate). The sheet is then squeezed between two rolls with a nip pressure of 50 p.s.i.g. (3.5 kg./cm. at a speed of 1.5 yd./min. (1.4 rn./min.) and dried in a circulating hot air oven for 45 minutes at 93 C. The sheet is then tufted at the following conditions:

Type pile Loop.

I 7 The bond strength, variance and bond concentration of the bonded sheets and the properties of the tufted sheets are summarized below:

Characteristics of bonded sheet:

18 Example XIII A method was developed to measure tufting response in nonwoven sheets by determining the number of broken filament ends on single-needle tufting, without yarn, at a needle speed on impact of about 100 ft./min. (30.5 m./ min). In order to obtain comparable results, the same slightly blunted needle is used in all tests. In order to compare lubricants, tests are made on samples of the same nonwoven sheet. The broken filament ends in the tufting holes are determined by delaminating the sheet in the area of the hole into at least 4 thin layers. The layers are mounted on a slide under immersion oil and the broken filaments are counted under a microscope. Polarized light is useful in improving visibility and ease of counting. E am le XII Using the above method, a nonwoven sheet with a unit x P weight of 3.2 oz./yd. (108 g./m. and composed of 8 d.p.f. (0.9 tex) oriented isotactic polypropylene filaments A nonwoven web is prepared with oriented polypropylene filaments having low-oriented sections along the fiber Such as P p y method f EX mple IV, 1s used length. The polypropylene fil are 7 denier (078 for comparing the elfectlveness of varlous lubrlcants. This tex) per filament and have a tenacity of 4.11 g. ,d i h sheet, when lubricated with a mrxture of methyl hydrogen high-oriented sections and are 15.5 denier (1.7 teX) per P91YS11Xane.and dlmethyl Polyslloxane and tufted as filament and have a zenacfiy of L74 gpd. in the viously descrlbed, has a tufted-grab-tensile strength( crossoriented sections. The Web is prepared as follows: Polyg f duectlon) 92 3 5 propylene filaments are spun through a -hole spinneret 3 8 e ests i Came as 0 1X 5 at a rate of 18 g./min. total. Each spinneret hole is 0.015 Z Samp es of Sheet are umformly m (0038 cm.) in diameter and the temperature of the coated w th the lubricant at a level 1n excess of the maxi- Spinneret is C The filaments are led to a heated mum WhlCh the filaments can ultimately absorb. One or feed roll with filmed-25 in. (3.17 cm.) grooves cut out 30 two additional sets of samples are coated at lubricant 120 apart. The filaments are in contact with the roll for levels less than h maxlmum absorptlons' These samples The Surface temperature of the roll is 0 The are then treated in an oven at 100 C. for times from a roll is operated with a surface speed of 243 yd./min. few f up 1 m case Polysiloxanes (222 m /min The filaments leaving the heated feed to obtam sheets with various ratios of lubricant absorbed roll are then passed 3 wraps around an idler roll/draw to lub ncant the Surface of the filaments sample? are roll System Operating cold with a Surface Speed of 858 then 1mmed1ately tufted and analyses of the lubricant yd./min. (784 m./min.). The filaments are then laid down (the amount on the f the amount absorbed as nonwoven web of randomly distributed continuous the loss hung the heatmg Step) are made at the filaments as in Example XI. The filamentary Web is of tufting. These analyses are based on a 10-second acetone bonded as in Example XI with saturated steam at a pres- 40 Wash (methyl ethyl ketone for thee/ts Wlth mmeral 011 Sure of 70 (4.9 g gy The bonded Sheet is as lubrrcant) to remove the lubrrcantfrom the surface lubricated and then tufted by the procedure of Example of the filaments without extracting significant amounts of XI. The sheet characteristics and the tufted-sheet propthat which absorbed The filament breakage 1S taken erties are summarizedbelow: as the average from 3 holes. From plots of the data so obtained, the amounts of lubricant absorbed and the tuftt ing responses can be compared. charac enstics of bonded sheet It is found that tuftmg response is independent of the Unlt Welght Y amount of lubricant absorbed by the filaments and of the heat treatment, but is dependent on the amount of lubri- Average bond strength (S) 2.40 g. cant on the surface of the filaments. The results are sum- Bond strength variance (a 17- marized below and show the amount of lubricant ab- No. bonds/cm. (N 7.59 10 g./crn. sorbed after the heat treatment, the amount of lubricant Filament-breaking strength (f) 25.7 g. required on the surface to reduce the number of broken Nbg/f 2 95 103/ 8 filament ends per hole to 100, and the minimum number Properties f tufted h of broken filament ends per hole at higher levels of lubri- G b il 165 1b, (75 kg), cant on the surface. Wlth no lubricant, there are more than Dye-beck-width loss 3.5%. 250 broken filament ends per hole.

Percent Lubri- Lubricant Abcant on Sur- Minimum N o. Lubricant sorbed, percent, face, at 100 of Broken Filabased on sheet Broken Filament Ends ment Ends Dimethyl polysiloxane 0. 7 O. 2 45 (1. 25%) Diootyl sebacate 2 2 40 (3. 0%) Z-Ethylhexyl sebacate. 3.1 1.4 (4.0%) Acetyl tri-2-ethy1hexyl tra 2.8 1.5 (4.0%) gltgtonltgs 21 3.0 1.1 65 (4.0%

11 um gotassium n-octyl phosphate i 0 0 (2 0%) Figures in parenthese represent amounts of lubricant on surface at minimum number of broken filament ends.

119 V In additional tests with a similar but more heavily bonded 3 oz./yd. (1'02 g./m. nonwoven sheet of 8 d.p.f. (0.9 tex) oriented isotactic polypropylene filaments, the following results are obtained:

invention provide substantial advantages. The backings can be made thinner, so that more effective use of the tufting yarn is possible. The backings are highly resistant to damage by tufting needles. And, most importantly, the finished 1 Figures in parentheses represent amounts of lubricants on surface at minimum number of broken filament ends.

2 Approximately 0.4% mineral oil (based on the sheet) is also lost by volatilization. 3 Level of 100 broken filament ends per hole not reached with the nonpolar mineral oil.

These results indicate the superior performance of the polysiloxanes as lubricants and the advantages of the low amount required for good tufting response and the low level of absorption. Mineral oil is less effective than the polar lubricants, as evidenced both by the amount of lubricant required and the minimum level of broken filaments ends reached. Because of this lower effectiveness, coupled with the high absorption level, nonpolar mineral oil is not considered to be a satisfactory lubricant for use in this invention.

I While the examples above describe the preparation of highly desirable embodiments of the present invention, it is obvious that suitable modifications can be made without departing from the teachings set forth here. Specifically, it is possible to use for either primary or secondary backings, bonded sheets having a unit weight in the range of about 1 to 5 oz./yd. (34 to 170 g./m. and filaments having a denier of from about 3-15 (0.31.7 tex) and preferably from 5 to (0.5 to 1.1 tex). If a denier below 3 (0.3 tex) is employed, the sheet is found to break on tufting, leaving perforated sections. Deniers higher than (1.7 tex) do not give sufiicient cover to permit the tuft to be held firmly within the sheet.

The nowo ven sheets of this invention are highly effective as primary carpet backings because of the mobility of the constituent filaments. If lubrication is omitted, the filaments within the bonded nonwoven sheet lack suflicient mobility to permit tufting without damage. During the tufting operation, this mobility is exhibited by the fact that the bonds break rather than the individual filaments. After tufting, therefore, the sheet is at least partially debonded. This causes no difficulty in the tufted area since the tufting yarns reinforce the sheet. In the untufted edges of the sheet adjacent to the tufted area, however, delamination and fuzzing can occur, particularly during the piece dyeing of the tufted carpet in the dye beck. These edges are needed in the subsequent tentering step and cannot be used for this purpose when they have become badly frayed.

The edges of the nonwoven sheet can be stabilized against delamination andfuzzing in the operations subsequent to tufting by methods which provide more extensive bonding of the edges. One such method uses a hot needle assembly or spark-bonding technique to provide regions of fused-periphery perforations as described in copending Sands application, Ser. No. 279,579, filed May 10, 1963. Another operable method involves application of a latex binder or hot melt adhesive to the untufted edges. Contact of the edges with a smooth, hot metallic surface provides a glazed surface which is resistant to fuzzing and delamination. The edges can also be stabilized by tufting with waste yarn. This portion is finally trimmedand discarded.

As already indicated, the carpet backings of the present carpets have a much higher degree of dimensional stability and freedom from shrinkage than do carpets made with jute or other cellulosic backing.

The lubricated, bonded nonwoven sheets of this invention can also be used in other tufted products, such as chenille bedspreads, bath mats, scatter rugs, pile linings and the like.

What is claimed is:

1. A lubricated self-bonded nonwoven sheet of randomly dispersed, overlapping and intersecting highly crystalline and oriented synthetic continuous filaments of polyrners of the group consisting of isotactic polypropylene, linear polyethylene, crystalline copolymers of at least propylene or ethylene with up to 25% by weight of other copolymerizable monomers and mixtures of isotactic polypropylene or linear polyethylene with up to 25 by weight of other polymers, said filaments having a denier between 3 and 15 and being substantially separate and independent from each other throughout the sheet except at crossover points, the said filaments being self-bonded at a multiplicity of such intersection points and possessing a birefringence that is at least 40% of the maximum birefringence, said sheet having an average edge bond count of between about 30 and bonds per filaments and containing from about 0.3% to about 5% by weight of a lubricant that is inert to the filaments, said lubricant being selected from the group consisting of methyl hydrogen polysiloxane, dimethyl polysiloxane, 2-ethylhexyl silicate, 2-ethylhexyl sebacate, dioctyl sebacate, acetyl Z-ethylhexyl citrate, refined coconut oil, potassium olcate, potassium n-octyl phosphates, diethanolamine salts of C C alkyl hydrogen phosphates and mixed n-octyl fi-hydroxy-ethyl esters of phosphoric acid.

2. The product of claim 1 wherein the lubricant wets the filaments and remains substantially on the filament surface.

3. The product of claim 1 where the lubricant is a polysiloxane.

4. The product of claim 1 wherein the synthetic filaments are isotactic polypropylene.

5. A method of preparing a tufted carpet comprising, tufting pile yarns in through a lubricated self-bonded nonwoven sheet of randomly dispersed, overlapping and intersecting, highly crystalline and oriented synthetic continuous filaments of polymers of the group consisting of isotactic polypropylene, linear polyethylene, crystalline copolymers of at least 75% propylene or ethylene with up to 25% by weight of other copolymerizable monomers and mixtures of isotactic polypropylene or linear polyethylene with up to 25% by weight of other polymers, said filaments having a denier between 3 and 15 and being substantially separate and independent from each other through out the sheet except at crossover points, the said filaments being self-bonded at a multiplicity of such intersection points and possessing a birefringence that is at least 40% of the maximum birefringence, said sheet having an average edge bond count of between about 30 and 80 bonds per 100 filaments and containing from about 0.3% to about by weight of a lubricant that is inert to the filaments, said lubricant being selected from the group consisting of methyl hydrogen polysiloxane, dimethyl polysiloxane, 2- ethylhexyl silicate, Z-ethylhexyl sebacate, dioctyl sebacate, acetyl 2-ethylhexyl citrate, refined coconut oil, potassium oleate, potassium n-octyl phosphates, diethanolamine salts of C -C alkyl hydrogen phosphates and mixed n-octyl ,B-hydroxyethyl esters of phosphoric acid.

6. A lubricated bonded nonwoven sheet comprising a matrix of synthetic organic fibers of polymers of the group consisting of isotactic polypropylene, linear polyethylene, crystal-line copolymers of at least 75% propylene or ethylene with up to 25% by weight of other copolymerizable monomers and mixtures of isotactic polypropylene or linear polyethylene with up to 25 by weight of other polymers, said fibers having a breaking strength of at least 7 grams, said fibers being inter-connected at a multiplicity of points throughout the sheet, by bonds having a strength greater than 0.1 gram, the average strength of these bonds being at least 0.9 gram and less than the matrix fiber breaking strength, the bond strength distribution being characterized by a variance of at least 4, the number of bonds being such that the product of the number of bonds per cubic centimeter and the average bond strength is greater than 5x10 g./crn. and this product divided by the fiber breaking strength is less than 9 1O /cm. said sheet containing from about 0.3% to about 5% by weight of a lubricant that is inert to the filaments, said lubricant being selected from the group consisting of methyl hydrogen polysiloxane, dimethyl polysiloxane, Z-ethylhexyl silicate, 2-ethylhexyl sebacate, dioctyl sebacate, acetyl 2- ethylhexyl citrate, refined coconut oil, potassium oleate, potassium n-octyl phosphates, diethanolamine salts of C -C alkyl hydrogen phosphates and mixed n-octyl B-hydroxy-ethyl esters of phosphoric acid.

7. The product of claim 6 wherein the lubricant wets the filaments and remains substantially on the filament surface.

8. The product of claim 6 wherein the lubricant is a polysiloxane.

9. The product of claim 8 wherein the matrix filaments are isotactic polypropylene.

10. A method of preparing a tufted carpet comprising tufting pile yarns in through a lubricated bonded nonwoven sheet comprising a matrix of synthetic organic fibers of polymers of the group consisting of isotactic polypropylene, linear polyethylene, crystalline copolymers of at least 75 propylene or ethylene with up to 25% by weight of other copolymerizable monomers and mixtures of isotactic polypropylene or linear polyethylene with up to 25 by weight of other polymers, said fibers having a breaking strength of at least 7 grams, said fibers being inter-connected at a multiplicity of points throughout the sheet, by bonds having a strength greater than 0.1 gram, the average strength of these bonds being at least 0.9 gram and less than the matrix fiber breaking strength, the bond strength distribution being characterized by a variance of at least 4, the number of bonds being such that the prodnot of the number of bonds per cubic centimeter and the average bond strength is greater than 5x10 g./cm. and this product divided by the fiber breaking strength is less than 9 10 /cm. said sheet containing from about 0.3% to about 5% by Weight, of a lubricant that is inert to the filaments, said lubricant being selected from the group consisting of methyl hydrogen polysiloxane, dimethyl polysiloxane, 2-ethylhexyl silicate, 2-ethylhexyl sebacate, dioctyl sebacate, acetyl Z-ethylhexyl citrate, refined coconut oil, potassium oleate, potassium n-octyl phosphates, diethanolamine salts of (I -C alkylhydrogen phosphates and mixed n-octyl fi-hydroxy-ethyl esters of phosphoric acid to achieve stitched engagement therewith and locking the pile yarns in place with an adhesive.

References Cited UNITED STATES PATENTS 2,839,158 6/1958 Reinauer -524 2,862,251 12/1958 Kalwaites 161-109 X 2,913,803 11/1959 Dodds 16165 2,999,297 9/ 1961 Schwartz 28-74 X 3,049,466 9/1962 Erlich l61-252 X 3,081,501 3/1963 Kalwaites 19-461 3,140,198 7/1964 Dawson et al. 117-139.5 X

ALEXANDER WYMAN, Primary Examiner. JACOB H. STEINBERG, Examiner.

D. H. ROBESON, M. A. LITMAN, Assistant Examiners. 

1. A LUBRICATED SELF-BONDED NONWOVEN SHEET OF RANDOMLY DISPERSED, OVERLAPPING AND INTERSECTING HIGHLY CRYSTALLINE AND ORIENTED SYNTHETIC CONTINUOUS FILAMENTS OF POLYMERS OF THE GROUP CONSISTING OF ISOTATIC POLYPROPYLENE, LINEAR POLYETHYLENE, CRYSTALLINE COPOLYMERS OF AT LEAST 75% PROPYLENE OR ETHYLENE WITH UP TO 25% BY WEIGHT OF OTHER COPOLYMERIZABLE MONOMERS AND MIXTURES OF ISOTACTIC POLYPROPYLENE OR LINEAR POLYETHYLENE WITH UP TO 25% BY WEIGHT OF OTHER POLYMERS, SAID FILAMENTS HAVING A DENIER BETWEEN 3 AND 15 AND BEING SUBSTANTIALLY SEPARATE AND INDEPENDENT FROM EACH OTHER THROUGHOUT THE SHEET EXCEPT AT CROSSOVER POINTS, THE SAID FILAMENTS BEING SELF-BONDED AT A MULTIPLICITY OF SUCH INTERSECTION POINTS AND POSSESSING A BIREFRINGENCE THAT IS AT LEAST 40% OF THE MAXIMUM BIREFRINGENCE, SAID SHEET HAVING AN AVERAGE EDGE BOND COUNT OF BETWEEN ABOUT 30 AND 80 BONDS PER 100 FILAMENTS AND CONTAINING FROM ABOUT 0.3% TO ABOUT 5% BY WEIGHT OF A LUBRICANT THAT IS INERT TO THE FILAMENTS, SAID LUBRICANT BEING SELECTED FROM THE GROUP CONSISTING OF METHYL HYDROGEN POLYSILOXANE, DIMETHYL POLYSILOXANE, 2-ETHYLHEXYL SILICATE, 2-ETHYLHEXYL SEBACATE, DIOCYTL SEBACAE, ACETYL 2-ETHYLHEXYL CITRATE, REFINED COCONUT OIL, POTASSIUM OLEATE, POTASSIUM N-OCTYL PHOSPHATES, DIETHANOLAMINE SALTS OR C8-C12 ALKYL HYDROGEN PHOSPHATES AND MIXED N-OCTYL B-HYDROXY-ETHYL ESTERS OF PHOSPHORIC ACID. 